Photek Ltd has developed a new time resolved ion imaging system. Using novel microchannel plate (MCP) gating electronics we have developed extremely short imaging windows for a large active area. We have also developed a method for extracting a timing signal from the phosphor screen of the detector that gives an accurate electronic signal corresponding to each ion event.
We have developed a high voltage pulse generator that is specifically designed to couple the pulse onto an MCP stack that already has a voltage applied but is below the threshold for ion detection. This gating pulse pushes the MCPs into their working voltage for a short gating window.
Using the model of a sealed tube image intensifier with an input window coated in a visible light photocathode and a short laser pulse, we have been able to visually demonstrate the progression of the gating pulse across the MCP surface.
Using high voltage MOSFETs we have developed an MCP gating unit that generates a minimum width of 9 ns for fixed pulse amplitude of +500 V. This voltage differential is enough to move the MCP from a state where it generates very little signal to a full working voltage. We have measured a difference of four orders of magnitude in response between the ON and OFF states.
The new gating unit combined with an integrated camera system has demonstrated an imaging window of 3.5 ns FWHM for a full 25 mm working diameter with an r.m.s jitter of 80 ps from the trigger pulse. Due to the non-linear nature of MCPs the optical window is shorter than the electronic pulse. The gate width is fully adjustable and the gate unit is able to operate up to 1 KHz repetition rate. The position resolution of the system is limited by the pore size of the MCP (typically 10 µm).
The extracted timing signal turns the system into a time-of-flight (TOF) detector with 3 ns resolution.
For project updates and product information go to:
Contact: ian.cox@photek.co.uk
Tel. +44 (0)1424 850555